5.8.2 Special Files for Network Communications

gawk programs
can open a two-way
TCP/IP connection, acting as either a client or a server.
This is done using a special file name of the form:

/net-type/protocol/local-port/remote-host/remote-port

The net-type is one of ‘inet’, ‘inet4’, or ‘inet6’.
The protocol is one of ‘tcp’ or ‘udp’,
and the other fields represent the other essential pieces of information
for making a networking connection.
These file names are used with the ‘|&’ operator for communicating
with a coprocess
(see Two-way I/O).
This is an advanced feature, mentioned here only for completeness.
Full discussion is delayed until
TCP/IP Networking.